1. Field of the Invention
The present invention relates generally to a polyelectrolytic battery having a positive electrode, a negative electrode and a polyelectrolyte and more particularly, to a polyelectrolytic battery featuring a great battery capacity such as not reduced by repeated chargings and dischargings of the battery, thus offering an excellent charge/discharge cycle characteristic.
2. Description of the Related Art
Conventionally, it has been general practice in the art to utilize the aqueous type or non-aqueous type electrolytic solutions as the electrolytes of batteries. More recently, the spotlight is on the polyelectrolytic battery in which a polyelectrolyte composed of a high polymer replaces such electrolytic solutions.
The polyelectrolytic battery utilizing the polyelectrolyte suffers less solution leakage and corrosion than the prior-art batteries utilizing the electrolytic solutions. The polyelectrolytic battery provides further merits such as of simple construction which therefore, is easy to fabricate.
Unfortunately, however, the battery utilizing the polyelectrolyte normally has a low electrolytic conductivity and a poor adhesion between the electrodes and the polyelectrolyte. This results in a low battery capacity. The polyelectrolytic battery particularly suffers capacity reduction during discharge at high current (high-rate discharge). Furthermore, this battery presents greater decrease in the capacity as the charging and discharging thereof are repeated.
Such an electrolytic battery may be configured in various ways. For example, the polyelectrolytic battery may include a polyelectrolytic film composed of a high polymer impregnated with lithium salt or the like, or a polyelectrolytic film composed of a high polymer impregnated with an electrolytic solution composed of a mixture of a solute, such as lithium salt or the like, and a solvent, which polyelectrolytic film is interposed between the positive and negative electrodes. Otherwise, the above polyelectrolyte is impregnated into fine cavities of a porous film which is then interposed between the positive and negative electrodes.
A problem exists with the polyelectrolytic battery in which the porous film with the polyelectrolyte impregnated into its cavities is interposed between the positive and negative electrodes. That is, when the positive or negative electrode undergoes volumetric change due to the charging or discharging of the battery, the porous film acts to suppress the volumetric change of the positive or negative electrode, thus inhibiting the positive or negative electrode from sufficiently absorbing lithium ions or the like. This results in reduction of charge/discharge capacity or lowered charge/discharge cycle characteristic of the polyelectrolytic battery.